| Message ID | 20210723094943.7203-1-joyce.kong@arm.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Thomas Monjalon |
| Headers | show |
| Series | [v2] doc: update atomic operation deprecation | expand |
| Context | Check | Description |
|---|---|---|
| ci/intel-Testing | success | Testing PASS |
| ci/Intel-compilation | success | Compilation OK |
| ci/github-robot | success | github build: passed |
| ci/checkpatch | success | coding style OK |
23/07/2021 11:49, Joyce Kong: > Update the incorrect description about atomic operations > with provided wrappers in deprecation doc[1]. > > [1]https://mails.dpdk.org/archives/dev/2021-July/213333.html > > Fixes: 7518c5c4ae6a ("doc: announce adoption of C11 atomic operations semantics") > Cc: stable@dpdk.org > > Signed-off-by: Joyce Kong <joyce.kong@arm.com> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com> Applied, thanks. Considering all the questions regarding usage of atomics, I still think we need a documentation about their correct use.
> -----Original Message----- > From: Thomas Monjalon <thomas@monjalon.net> > Sent: Saturday, July 31, 2021 3:27 PM > To: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>; Ruifeng Wang > <Ruifeng.Wang@arm.com>; Joyce Kong <Joyce.Kong@arm.com> > Cc: stephen@networkplumber.org; mdr@ashroe.eu; dev@dpdk.org; nd > <nd@arm.com>; stable@dpdk.org > Subject: Re: [dpdk-dev] [PATCH v2] doc: update atomic operation deprecation > > 23/07/2021 11:49, Joyce Kong: > > Update the incorrect description about atomic operations with provided > > wrappers in deprecation doc[1]. > > > > [1]https://mails.dpdk.org/archives/dev/2021-July/213333.html > > > > Fixes: 7518c5c4ae6a ("doc: announce adoption of C11 atomic operations > > semantics") > > Cc: stable@dpdk.org > > > > Signed-off-by: Joyce Kong <joyce.kong@arm.com> > > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com> > > Applied, thanks. > > Considering all the questions regarding usage of atomics, I still think we need a > documentation about their correct use. I think few things to document are: 1) Use of __atomic_add_fetch vs __atomic_fetch_add 2) Using __ATOMIC_RELAXED for statistics 3) Using rte_atomic_thread_fence API Anything else? >
02/08/2021 19:22, Honnappa Nagarahalli: > From: Thomas Monjalon <thomas@monjalon.net> > > 23/07/2021 11:49, Joyce Kong: > > Considering all the questions regarding usage of atomics, I still think we need a > > documentation about their correct use. > > I think few things to document are: > 1) Use of __atomic_add_fetch vs __atomic_fetch_add > 2) Using __ATOMIC_RELAXED for statistics > 3) Using rte_atomic_thread_fence API That's a good list. Let's start with that please. I would like an explanation about when full barrier may be used.
diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst index 9584d6bfd7..a4f350fa09 100644 --- a/doc/guides/rel_notes/deprecation.rst +++ b/doc/guides/rel_notes/deprecation.rst @@ -19,16 +19,18 @@ Deprecation Notices * rte_atomicNN_xxx: These APIs do not take memory order parameter. This does not allow for writing optimized code for all the CPU architectures supported - in DPDK. DPDK will adopt C11 atomic operations semantics and provide wrappers - using C11 atomic built-ins. These wrappers must be used for patches that - need to be merged in 20.08 onwards. This change will not introduce any - performance degradation. + in DPDK. DPDK has adopted the atomic operations from + https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html. These + operations must be used for patches that need to be merged in 20.08 onwards. + This change will not introduce any performance degradation. * rte_smp_*mb: These APIs provide full barrier functionality. However, many - use cases do not require full barriers. To support such use cases, DPDK will - adopt C11 barrier semantics and provide wrappers using C11 atomic built-ins. - These wrappers must be used for patches that need to be merged in 20.08 - onwards. This change will not introduce any performance degradation. + use cases do not require full barriers. To support such use cases, DPDK has + adopted atomic operations from + https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html. These + operations and a new wrapper ``rte_atomic_thread_fence`` instead of + ``__atomic_thread_fence`` must be used for patches that need to be merged in + 20.08 onwards. This change will not introduce any performance degradation. * lib: will fix extending some enum/define breaking the ABI. There are multiple samples in DPDK that enum/define terminated with a ``.*MAX.*`` value which is
Update the incorrect description about atomic operations with provided wrappers in deprecation doc[1]. [1]https://mails.dpdk.org/archives/dev/2021-July/213333.html Fixes: 7518c5c4ae6a ("doc: announce adoption of C11 atomic operations semantics") Cc: stable@dpdk.org Signed-off-by: Joyce Kong <joyce.kong@arm.com> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com> --- doc/guides/rel_notes/deprecation.rst | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-)